The invention relates to supplying electricity to electrical equipment in an aircraft engine and/or its surroundings.
The field of application of the invention is more particularly that of airplane engines, in particular gas turbine engines. Nevertheless, the invention is also applicable to helicopter engines.
The term “electrical equipment in an aircraft engine or in its surroundings” is used herein to cover not only electrical equipment that is useful for enabling the engine to operate, but also electrical equipment associated with the engine nacelle, such as, for example, de-icing or anti-icing electrical circuits such as circuits for nacelle anti-icing (NAI) or actuators for use in a thrust-reverse cowl opening system (TRCOS) or electromechanical actuators for use in electrical thrust-reverse actuation control (ETRAC) for a gas turbine airplane engine, or even circuits associated with the wing carrying the engine, such as, for example, airplane wing de-icing or anti-icing electrical circuits.
A traditional scheme for producing and distributing electricity from a gas turbine airplane engine is shown in FIG. 3.
Two generators 111a, 111b (or more than two for the purposes of redundancy or of optimizing the generation of electricity, depending on the application under consideration) are mounted on an accessory gearbox 113 that is mechanically coupled to a turbine shaft of the engine. The generators 111a, 111b are typically starter/generators (S/G) comprising a synchronous generator that is associated with excitation and that delivers an alternating voltage at a frequency that varies as a function of engine speed, the exciter assembly and the synchronous generator being controlled to operate in a synchronous motor mode when starting the turbine.
The alternating voltages delivered by the generators 111a, 111b are conveyed by lines 115a, 115b to an electrical network 117 for distributing electricity on board the airplane, referred to as the “on-board network”. A circuit 119 of the on-board network and connected to the lines 115a, 115b delivers alternating current (AC) at a regulated alternating voltage, typically at 115 volts AC (Vac) or 230 Vac, on one or more distribution buses. The circuit 119 also powers a voltage converter 121 that delivers a regulated direct current (DC) voltage, typically 270 volts DC (Vdc) or ±270 Vdc on one or more buses. The voltages delivered by the circuits 119 and 121 power different electrical loads on board the airplane, mainly in the fuselage zone thereof.
Associated with the engine, a full authority engine control unit (ECU) 143 is powered by a generator 127 such as a permanent magnet generator or permanent magnet alternator (PMA) mounted on the gearbox 113. The ECU 143 is also connected to one of the circuits 119, 121 e.g. the regulated alternating voltage circuit 119, so as to enable it to be powered properly so long as the engine has not reached a speed that is sufficient for enabling the PMA 127 to deliver the required electricity, or in the event of the PMA failing. The ECU 143 makes use of the electricity it receives for enabling its components to operate and for exciting various elements of the engine such as sensors or probes, actuators or servo-valves that require limited amounts of electrical power.
At present, there is a trend towards replacing hydraulic energy more and more with electrical energy for actuating various pieces of electrical equipment in an aircraft engine or in its environment. For example, some airplanes are fitted with electrically-actuated thrust reversers 147. Thus, the circuit includes AC/DC converters 133 having inputs connected to the on-board network 117 via electrical power supply lines 145, 149, 151 and having outputs connected to such an electrical thrust reverser 147 and also to static equipment, such as circuits 153, 155 for de-icing the engine nacelle and the wing carrying the engine.
The delivery of electricity from the network on board the aircraft to the various loads external to the fuselage by means of power supply lines which need to be made very safe and to be insulated lines represent weight and bulk that are considerable, running the risk of becoming dimension-determining or even prohibitive if the amount of equipment to be powered increases, and the delivery itself presents electrical losses that are not negligible.